Applicants claim priority under 35 U.S.C. xc2xa7119 of German Application No. 199 51 084.9 filed Oct. 23, 1999. Applicants also claim priority under 35 U.S.C. xc2xa7120 of PCT/DE00/03508 filed Sep. 30, 2000. The international application under PCT article 21(2) was not published in English.
This invention relates to a liquid filter, especially an oil filter, for cleaning lubricating oil, especially for internal combustion engines in motor vehicles, having the features of the definition of the species of claim 1.
German Patent 39 03 675 C2 describes an oil filter of this type, having a filter housing which is essentially upright when in stalled and which contains a filter receiving space to accommodate a ring-shaped filter insert in an upper section and which contains in a lower section an inlet channel for uncleaned oil and an outlet channel for purified oil. The inlet channel connects an inlet line of the oil filter, which is connected to a pressure side of an oil pump, to a crude side of the ring-shaped filter insert in the filter receiving space. The outlet channel connects a clean side of the ring-shaped filter insert in the filter receiving space to an outlet line of the oil filter communicating with the lubricant sites of an internal combustion engine.
A liquid filter of the type defined in the preamble is essentially known from European Patent Application 0 874 140 A1 and in addition to the features mentioned above, it has an oil cooler which is inserted into an oil cooler receiving space designed in the lower section of the filter housing and is screwed to the filter housing. The oil cooler contains the outlet channel and remains in the filter housing when the ring-shaped filter insert is changed.
U.S. Pat. No. 5,814,215 describes another liquid filter, where a central supporting element is attached to the inside of a cover which is screwed removably onto the filter housing. This carrier element is designed internal groove in an axial section near the cover. The ring-shaped filter insert can be attached to the carrier element on the side facing away from the cover. The filter housing has a central recess like a blind hole to which the return line is connected centrally at the bottom and the drain line is connected at the side above it. The carrier element has an axial section which projects axially above the ring-shaped filter insert at a distance from the cover, penetrating into the recess when the cover is screwed onto the filter housing. The projecting axial section has on the free end a sealing stopper for tightly sealing the return line. The axial section of the carrier element penetrating into the recess also has a sealing section which seals the recess with respect to the interior of the filter housing above the drain line. Within the carrier element, a flow path is achieved which connects the clean side of the interior of the axial section designed as an inner groove to the recess in the housing. To change the ring-shaped filter insert, the cover is unscrewed from the filter housing, lifting the carrier element connected to it. In this way, the sealing stopper is removed from the return line, so that the filter housing can be emptied completely before removing the cover. After removing the carrier element from the filter housing, the ring-shaped filter insert on the carrier element can be replaced.
With the known liquid filters, the filter housing is manufactured in one piece with the channels integrated into it as an injection molded part. The inside of the housing must then be finished to provide a smooth surface for gaskets, for example. Likewise, careful machining of the surface is necessary to permit insertion of the ring-shaped filter insert here, so that its central interior can form a tight seal with the corresponding channel, namely the outlet channel on the clean end.
The present invention is concerned with the problem of designing a filter of the type defined in the preamble with regard to simplified machining.
This problem is solved according to this invention by a liquid filter having the features of claim 1.
This invention is based on the general idea of combining in a separately manufactured function carrier insert the parts of the filter housing which are manufactured in one piece together with the filter housing in the case of a traditional filter housing and which must be finished to fulfill their function. On the one hand, this yields the possibility of external finishing of these function elements, while on the other hand, the function carrier insert can also be manufactured in such a way that finishing can be omitted. For example, if the function carrier insert is made of plastic, it may be manufactured by an injection molding method, for example. The resulting surface quality is sufficiently high so that finishing can be omitted in most cases.
The function elements integrated into the function carrier insert include at least the outlet channel which connects the clean side of the ring-shaped filter insert in the filter receiving space to the outlet line of the liquid filter. Likewise, the following function elements can be integrated into the function carrier insert: the inlet channel connecting the inlet line of the liquid filter to the crude side of the ring-shaped filter insert in the filter receiving space and/or an emptying channel that allows the liquid to flow out of the filter receiving space and/or a return-flow-blocking valve which is provided with the inlet channel and/or a pressure-regulating valve connecting the outlet channel to the emptying channel, as a function of pressure, and/or a bypass valve connecting the inlet channel to the outlet channel as a function of pressure. The more function elements of the filter housing are integrated into the function carrier insert, the greater are the advantages of this invention, so that less finishing work is necessary for the filter housing.
In a preferred embodiment, a carrier holding space into which the function carrier insert is inserted in the lower section of the filter housing forms the inlet channel, so that the unclean liquid flows around the function carrier insert and the ring-shaped filter insert on the outside. Due to this design, the carrier holding space provided for the function carrier insert can be used as a function element, so that it has a double function in this regard.
Other important features and advantages of the device according to this invention are derived from the subclaims, the drawings and the respective description of the figures on the basis of the drawings.
It is self-evident that the features mentioned above and those to be explained below can be used not only in the combination indicated but also in other combinations or alone without going beyond the scope of the present invention.
A preferred embodiment of this invention is illustrated in the drawings and described in detail in the following description: